Merge branch 0.4.x into main

The following commits are merged using the default merge strategy.

0e509333bc Assert unique identifiers in JdbcRegisteredClientRepository
8b0e7578df Upgrade to JUnit 5

samples/default-authorizationserver/samples-default-authorizationserver.gradle

@@ -22,6 +22,6 @@ dependencies {
 
 	testImplementation "org.springframework.boot:spring-boot-starter-test"
 	testImplementation "org.springframework.security:spring-security-test"
-	testImplementation "junit:junit"
+	testImplementation "org.junit.jupiter:junit-jupiter"
 	testImplementation "net.sourceforge.htmlunit:htmlunit"
 }